What Is a TTML File?
Everything you need to know about TTML (Timed Text Markup Language), the XML-based subtitle format used by Netflix, Apple TV, and professional broadcast systems.
TTML (Timed Text Markup Language) is a W3C-standardized XML-based subtitle format. It is the delivery format required by Netflix, Apple TV/iTunes, and many broadcast systems. TTML supports rich styling, positioning, and metadata that plain-text formats like SRT cannot provide.
What Does TTML Stand For?
TTML stands for Timed Text Markup Language. It was developed by the W3C (World Wide Web Consortium) as a standardized way to represent timed text for video subtitles and captions. The format is formally specified in W3C TTML1 and its successor IMSC (TTML Profiles for Internet Media Subtitles and Captions).
How TTML Files Work
A TTML file is an XML document with a root <tt> element containing a <head> (metadata, styling) and a <body> (subtitle content). Each subtitle cue is a <p> element with begin and end attributes specifying timing in seconds (e.g., begin="1.500s"). Text within <p> can include <br/> tags for line breaks, <span> for inline styling, and various styling attributes.
When to Use TTML
TTML is required when delivering subtitles to Netflix, Apple TV/iTunes, or broadcast systems that follow EBU-TT or IMSC standards. It is also used in professional localization and captioning workflows where rich styling and metadata are needed. If you are working with consumer video players, SRT or VTT may be more appropriate.
TTML File Structure
<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/ns/ttml">
<body>
<div>
<p begin="0.500s" end="3.000s">First subtitle line</p>
<p begin="3.500s" end="6.000s">Second subtitle<br/>with a line break</p>
</div>
</body>
</tt>
Advantages of TTML
- W3C standard for timed text, ensuring cross-platform consistency
- Rich styling support: fonts, colors, sizes, positioning, alignment
- Required by Netflix, Apple TV/iTunes, and many broadcast systems
- XML structure enables validation and programmatic processing
- Supports metadata, roles, and language annotations
- Foundation for IMSC (industry-standard captioning profiles)
Limitations of TTML
- More complex than plain-text formats like SRT
- Larger file sizes due to XML overhead
- Not universally supported by consumer media players
- Requires XML knowledge to edit manually
- Different profiles (TTML1, IMSC, EBU-TT) can cause compatibility issues
Platforms That Use TTML
TTML Frequently Asked Questions
What is the difference between TTML and ITT?
ITT (iTunes Timed Text) is a profile of TTML used by Apple for iTunes and Apple TV. The XML structure is fundamentally the same as TTML, but ITT has additional metadata requirements specific to Apple's delivery specifications.
Can I convert SRT to TTML?
Yes. Use our SRT to TTML converter to transform plain-text SRT subtitles into TTML format. The conversion preserves all timing and text data, restructures them into XML, and escapes special characters.
Does TTML support styling?
Yes. TTML supports inline styling through XML attributes and nested elements. You can define styles in the <head> section using <style> elements and reference them, or apply styling directly on <p> and <span> elements.
What time format does TTML use?
TTML uses time expressions like begin="1.500s" (1.5 seconds). It also supports other expressions like HH:MM:SS.mmm format and frame-based timing, but the seconds-based format (e.g., 1.500s) is most common in practice.
Is TTML the same as IMSC?
IMSC (TTML Profiles for Internet Media Subtitles and Captions) is a standardized profile of TTML. All IMSC documents are valid TTML, but not all TTML documents conform to IMSC constraints. IMSC is the industry standard for streaming platform delivery.